ratio measurements in environmental samples by RNAA, ÂMS and direct y-X spectrometry. Intercomparison exercises

i2, I, is a natural long-lived isotope, with a half-life of 15.7 million years, also artificially produced in nuclear power plan! and released in liquid and gaseous effluents of nuclear fuel reprocessing plants. Due to the lack of environmental international reference material for 129 I, interlaboratory comparison exercises are very rare and validation of new measurement techniques is very difficult to achieve. This study presents three intercomparison exercises on the 129 I and 129ynil measurements using three different techniques : Radiochemical Neutron Activation Analysis, Accelerator Mass Spectrometry and direct y-X spectrometry associated with Ionic Chromatography. The first intercomparison was performed on a Fucus mmtiis sample, leading to propose it as a reference material. The others intercomparison exercises were performed on samples of different biological matrices, marine and terrestrial, presenting various 129 I activity levels. The different intercomparison exercises results showed a good agreement between the three, techniques on the considered environmental matrices, for samples with 129 I activity comprised between 0.2 and 200 Bq.kg"1 dry weight.